Individuals with HIV face serious risks from heavy drinking, including decreased immune function, poor medication adherence, and risk for liver damage, now a leading cause of mortality in HIV. For individuals with both HIV and hepatitis C virus (HCV), heavy drinking is particularly hazardous, as it limits HCV treatment and exacerbates liver damage. However, despite increasing recognition of the harms associated with drinking in HIV/HCV, little research has investigated possible explanations for this risky behavior, and no interventions exist specifically to reduce heavy drinking in HIV/HCV co-infected patients, who face the highest risk. In this K23 application, I propose a training and research program that will enable me to begin pursuing my long-term goal of advancing understanding and ability to intervene with heavy drinking in the high-risk group of patients with HIV and HCV. My training will focus on HIV and HCV (the diseases, co-infection, and treatment), clinical trials in medical populations, and biostatistics. I will obtain this training through courses and seminars offered by Columbia University Medical Center, as well as regular meetings with expert mentors and consultants. I will use this training to address short-term goals: to investigate factors underlying heavy drinking among patients with HIV (Aim 1a) and HIV/HCV (Aim 1b); to adapt and pilot test a drinking-reduction intervention for HIV/HCV co-infected patients (Aim 2), incorporating information from Aims 1a and 1b; and to develop an R01 proposal for a full clinical trial. For Aim 1a, I will use data from a large clinical trial to invetigate factors underlying heavy drinking among HIV patients. Applying drinking motive constructs from the larger alcohol literature that I have already validated in HIV patients, I will investigate the relationship between motives for drinking and abstaining and drinking outcomes in two different timeframes: as reported daily for 60 days, and from pre-intervention to 12 month follow-up. I will also investigate whether motives for drinking and abstaining change due to intervention. Further, I will investigate whether HIV patients in neighborhoods with permissive drinking norms differ from other patients on drinking, drinking motives, and response to intervention. For Aim 1b, I will use data from a large cross-sectional study of drug users to determine whether drinking differs by patient perceptions of health status and HIV and HCV severity. For Aim 2, I will adapt and pilot test an existing brief, technology- enhanced drinking-reduction intervention for HIV patients to be suitable for HIV/HCV co-infected patients. For this, I will incorporate findings fro Aims 1a and 1b, content from effective interventions for liver disease patients, and input from HIV primary care providers and patients. I will pilot test this intervention, and based on pilot results, design an R01 application for a full clinical trial for co-infected patients. This researc, which is only feasible through the training, research, and protected time offered by a K23 career development award, has strong potential to advance the understanding and ability to intervene with heavy drinking in HIV/HCV patients, a very hazardous behavior that poses substantial risks to patients' long-term survival.